Assessment of metabolism of equine morulae and blastocysts.

The research explores the metabolic processes of equine embryos at different stages, revealing that nutrient intake can potentially serve as an indicator of an embryo’s viability.

Overview of the Experiment

• The researchers investigated the nutrient uptake and metabolite production of equine (horse) embryos at two different developmental stages – the morula and blastocyst phases. Measurements were taken using non-invasive microfluorometry – a technique that uses fluorescence to analyze the cellular activity.

Findings Based on Embryo Development Stage

• In the morula stage (an early stage where the embryo is a solid ball of cells), the embryos were observed to consume equal amounts of two nutrients – pyruvate and glucose.
• In the early blastocyst stage (when a fluid-filled cavity forms within the embryo), a slight increase in glucose uptake was observed.
• By the expanded blastocyst stage (when the cavity has grown, forming distinct embryonic and placental cells), glucose became the main nutrient consumed. Specifically, expanded blastocysts took up five times more glucose than pyruvate.

Relationship Between Nutrient Uptake and Embryo Size

• Expanded blastocysts showed an exponential increase in glucose uptake and lactate (a byproduct of glucose metabolism) production in relation to their diameter and surface area.

Unaccounted Glucose Metabolism

• Notably, less than 50% of the glucose consumed was converted into lactate. This suggests that the equine blastocyst may be able to significantly oxidize glucose, meaning the cells may use glucose in energy production more efficiently.

Impact of Morphological Grade on Nutrient Intake

• Embryos with higher morphological grades (better-formed and more typical embryos) consumed more nutrients than embryos with poorer morphology (less well-formed).
• However, there was noticeable variation in nutrient consumption, even among blastocysts with the highest morphological grades.

Nutrient Uptake as a Viability Marker

• The researchers suggest that the variability in nutrient uptake, even amongst top-grade embryos, implies that nutrient uptake could potentially serve as a marker of embryo viability, helping breeders to select the most likely to survive and develop embryos.